1. Field of the Invention
The present invention relates in general to airbag passive restraint systems. In particular, the present invention relates to an improved arrangement for providing adaptive performance in airbag systems by selective venting of inflation gas from the housing of the system.
2. Description of the Related Art
Airbag passive restraint systems have become increasingly common in vehicles to protect the vehicle occupants during a collision. Such systems typically include a collision sensor to determine when a collision occurs, an inflator to provide a quantity of inflation gas upon receipt of a signal from the collision sensor, and a flexible cushion inflated by the inflation gas. The occupant of the vehicle impacts against this cushion to lessen the forces of the collision and reduce or eliminate injury.
One common arrangement for such a system is to provide an inflator received within the interior of a housing. The housing will include a opening or mouth providing access to the interior. The folded, uninflated cushion will also be received within the housing, with the mouth of the cushion secured to the housing such that the inflation gas may readily flow into the cushion. One or more covers will initially block the opening to the housing to protect the cushion and inflator. The cover(s) will open to permit the inflating cushion to exit the housing. These components taken together are typically referred to as a module, and are commonly employed for protection on the passenger side of the vehicle.
While this basic arrangement is serviceable, there has been a desire to provide airbag systems with adaptive performance. Adaptive performance is a variation in the module performance to provide the best protection to the occupant based upon the specific facts of the actual collision. For example, collisions vary in their severity, occupants vary in their weight, the position of the occupant in the seat (and therefore the distance from the inflating cushion) varies, the ambient temperature can affect gas output, etc. In adaptive performance a controller measures some or all of these variables (or others) and causes the module to inflate the cushion in a manner best suited to provide protection. For example, if the occupant is seated well forward in the seat, and is therefore close to the inflating cushion, the cushion may be inflated at a slower rate, so that the cushion does not injure the occupant during its inflation.